B.2 Varieties of Data Dependence

The three kinds of data dependence are described in the following way. The notation S1 , S2 , and SN is used to denote statement 1, statement 2, and statement N , respectively. In each example, S2 is dependent on S1 , due to variable X .

• Data dependence from an assignment to a use of a variable is called flow dependence (or true dependence):

  (S1):  X = 3
  (S2):  Y = X
  

• Data dependence from use of a variable to a later reassignment on that variable is called antidependence:

  (S1):  Y = X
  (S2):  X = 3
  

• Data dependence from an assignment of a variable to a later reassignment of that variable is called output dependence:

  (S1):   X = 3
  :
  (SN):   X = 4
  

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